The number of hydrogen atoms present in 5.4 g of urea is:

(Given: Molar mass of urea : $60 \mathrm{~g} \mathrm{~mol}^{-1}$

$\mathrm{N}_{\mathrm{A}}: 6.022 \times 10^{23}$ particles $\mathrm{mol}^{-1}$ )

When $1 \mathrm{dm}^3$ of CO₂ gas is passed over hot coke the volume of gaseous mixture after complete reaction at STP becomes $1.4 \mathrm{dm}^3$. The composition of the gaseous mixture at STP is :

Among the following, choose the ones with equal number of atoms.

A. 212 g of $\mathrm{Na}_2 \mathrm{CO}_3(\mathrm{~s})$ [molar mass $=106 \mathrm{~g}$ ]

B. 248 g of $\mathrm{Na}_2 \mathrm{O}(\mathrm{s})$ [molar mass $=62 \mathrm{~g}$ ]

C. 240 g of $\mathrm{NaOH}(\mathrm{s})$ [molar mass $=40 \mathrm{~g}$ ]

D. 12 g of $\mathrm{H}_2(\mathrm{~g})$ [molar mass $=2 \mathrm{~g}$ ]

E. 220 g of $\mathrm{CO}_2(\mathrm{~g})$ [molar mass $=44 \mathrm{~g}$ ]

Choose the correct answer from the options given below:

Dalton's Atomic theory could not explain which of the following?